Problem: $ { \left[\begin{array}{rrr}{2} & {4} & {-1} \\ {-2} & {4} & {2}\end{array}\right]+\left[\begin{array}{rrr}{2} & {2} & {-1} \\ {0} & {2} & {4}\end{array}\right] = {?} } $
Solution: To find the sum of two matrices, add the corresponding items between each matrix. ${\left[\begin{array}{rrr}{2}+{2} & {4}+{2} & {-1}+{-1} \\ {-2}+{0} & {4}+{2} & {2}+{4}\end{array}\right]}$ Now, simplify: ${\left[\begin{array}{rrr}{4} & {6} & {-2} \\ {-2} & {6} & {6}\end{array}\right]}$